JP3224267U - Motorcycle sprocket - Google Patents

Abstract

In a sprocket used for an off-road motorcycle or the like, mud or sand is prevented from adhering or biting between teeth of a roller chain or a sprocket. A discharge groove 4 inclined in a curved line on the upstream side in the rotational direction from the tooth bottom portion 24 toward the shaft center is provided on at least one of the front and rear surfaces of the disc-shaped sprocket SP for a motorcycle. To do. In the sprocket SP having the above configuration, the shape of the discharge groove 4 in a side view may be a square shape. [Selection] Figure 1

Description

  The present invention relates to a two-wheeled vehicle sprocket, and more particularly to a sprocket that is suitably used for off-road motorcycles such as motocross, trial, and enduro.

  As a method of transmitting power in a motorcycle, a method of transmitting power by linking an endless roller chain between a driving sprocket (drive sprocket) and a driven sprocket (driven sprocket) is usually used. . In such a power transmission system, the tooth part of the sprocket and the roller of the roller chain mesh with each other, and force is applied from the roller to the side surface of the tooth part (the side surface in the circumferential direction of the sprocket) or from the side surface of the tooth part.

  In off-road motorcycles that run on unpaved road surfaces, mud, sand, etc. are likely to adhere or bite between the teeth of the roller chain and sprocket. Part of the mud or sand that adheres to or bites between the teeth of the roller chain or sprocket may accumulate and solidify without being removed. When such a solidified material is formed between the teeth of the roller chain or sprocket, the tension of the chain roller increases. When the tension of the chain roller increases, the movement of the swing arm is restricted. Further, if the tension of the chain roller becomes too large, the chain roller may be broken. In addition, the shaft and bearings may be damaged. Further, when the solidified material becomes large, the chain roller may ride on the solidified material and be detached from the sprocket. In addition, the contact with the solidified material may promote wear of the teeth of the chain roller and the sprocket.

  Thus, for example, Patent Document 1 proposes forming a mud groove along the width direction on the tooth bottom of the sprocket and forming conical recesses leading to the mud groove on both side surfaces sandwiching the tooth bottom. ing. In Patent Document 2, it is proposed that a corrugated portion that swings in the thickness direction along the circumferential direction is formed on the outer peripheral portion of the sprocket, and teeth are formed on at least the outer end portion of the wave of the corrugated portion. Yes.

Japanese Utility Model Publication No. 1-12853 Japanese Patent Laid-Open No. 10-110806

  According to the proposed technique, it is considered that mud or sand adheres or gets stuck between the teeth of the roller chain and the sprocket to some extent, but further suppression is desired.

  The present invention has been made in view of such conventional problems. The purpose of the present invention is to prevent adhesion of mud and sand between roller chain and sprocket teeth in sprockets used for off-road motorcycles. The purpose is to further suppress biting.

  A sprocket according to the present invention that achieves the above-mentioned object is a disc-shaped sprocket for a motorcycle, and is inclined in a curved shape toward at least one of the front and back surfaces, from the tooth bottom to the shaft center and upstream in the rotational direction. It has a discharge groove.

  In the sprocket having the above configuration, the shape of the discharge groove in a side view may be a quadrangular shape.

  Further, in the sprocket having the above-described configuration, the bottom surface of the discharge groove may be linearly shallower from the tooth bottom portion toward the shaft center.

  In the sprocket having the above-described configuration, the inclination angle of the bottom surface of the discharge groove with respect to the front surface or the back surface on which the discharge groove is formed may be in the range of 10 ° to 20 °.

  In the sprocket having the above-described configuration, the discharge groove may have an arc shape, and two opposing side surfaces forming the discharge groove may be concentric circles having different radii.

  In the sprocket having the above-described configuration, the maximum width of the discharge groove may be 30% or more and 40% or less of the tooth profile pitch.

  In the sprocket having the above configuration, the discharge groove may be formed only on one side of the front surface and the back surface.

  According to the sprocket according to the present invention, even when mud or sand adheres or bites between the teeth of the roller chain or sprocket, when the sprocket is rotating, the sprocket is mainly driven by centrifugal force. When not rotating, the roller chain passes through a discharge groove formed on at least one side of the front and back surfaces of the sprocket, which is inclined by a curve in a curved shape from the root to the axial center toward the upstream in the rotational direction, mainly due to gravity. Mud and sand are eliminated from the meshing part of the sprocket and the teeth of the sprocket. This effectively suppresses accumulation and solidification of mud and sand between the teeth of the roller chain and the sprocket.

It is a front view which shows an example of the sprocket which concerns on this invention. It is an enlarged front view of the tooth | gear part 2 of the round frame A of FIG. It is a partial side view of the sprocket of FIG. FIG. 4 is a sectional view taken along line BB in FIG. 3.

  Hereinafter, the present invention will be described in more detail with reference to the drawings. However, the present invention is not limited to these embodiments.

  FIG. 1 is a front view showing an example of a sprocket according to the present invention, and FIG. 2 is an enlarged front view of a tooth portion 2 of a round frame A in FIG. Note that the sprocket SP shown in these drawings is used as a driven sprocket for a motorcycle (hereinafter sometimes simply referred to as “sprocket”).

  A sprocket SP shown in FIG. 1 includes a disc-shaped main body 1 having a predetermined thickness, and a plurality of teeth 2 formed on the outer periphery of the main body 1 at equal intervals in the circumferential direction.

  A shaft hole 15 having a predetermined diameter is formed in the center of the main body 1, and around the shaft hole 15, six fixing holes 16 for detachably attaching the sprocket SP to the motorcycle body are arranged at equal intervals in the circumferential direction. Is formed. The fixing hole is countersunk. In order to reduce the weight of the sprocket SP, a plurality of two types of circular lightening holes 17 and 18 having different diameters are formed around the shaft hole 15 of the main body 1 at predetermined intervals in the circumferential direction. Yes. In addition, the size, the number, the formation position, and the like of the shaft hole 15 and the fixing hole 16 are appropriately determined according to the specification of the motorcycle to which the sprocket SP is attached. Further, the shape and number of the lightening holes 17 and 18 are appropriately determined in consideration of the strength of the sprocket SP, etc., and the lightening hole 17 may have one type or three or more types. Of course, it does not matter even if it does not provide 18.

  A plurality of teeth 2 are formed on the outer periphery of the main body 1 at equal intervals in the circumferential direction. As shown in FIG.3 and FIG.4, the thickness of the front-end | tip part of the tooth | gear part 2 is gradually thin toward the radial direction outward. That is, on the front side and the back side of the tip portion of the tooth portion 2, arc-shaped inclined surfaces 25 a and 25 b that are formed radially outward and toward the thickness direction center are formed. Since the inclined surfaces 25a and 25b are formed at the tip of the tooth portion 2, when the roller chain starts to mesh with the tooth portion 2 of the sprocket SP, the roller chain slightly sways to the left and right with respect to the sprocket SP. Or, even if it approaches to one side, the biting of the sprocket SP of the roller of the roller chain into the tooth portion 2 is surely performed.

  1 and FIG. 2, the root portion 24 of the tooth portion 2 has a curved discharge that is convex in the rotational direction inclined toward the upstream side in the rotational direction from the bottom portion 24 toward the axial center of the sprocket SP. A groove 4 is formed. FIG. 2 shows an enlarged front view of the discharge groove 4.

As shown in FIG. 2, the discharge groove 4 has a substantially rectangular shape having a predetermined width W (shown in FIG. 3) and a predetermined length in a front view, and extends from the tooth bottom portion 24 toward the axial center of the sprocket SP. It is inclined upstream in the rotational direction (rightward in FIG. 2). More specifically, the shapes of the opposing side surface 41n and side surface 42n constituting the discharge groove 4n in FIG. 2 are determined on the basis of the tooth portion _2n-2 which is two previous upstream in the rotation direction, and the discharge groove 4n The length (terminal position) is determined on the basis of the immediately preceding tooth _2n-1 upstream in the rotational direction.

The leftmost discharge groove 4n in FIG. 2 will be described as an example. The center in the circumferential direction of the tooth tip 21 _n-2 and the sprocket SP in the tooth part 2 _n-2 two before the rotation direction upstream of the discharge groove 4n. straight L ₂ which connects the axial center of the the basis of the intersection IP ₂ between the pitch circle diameter Dp, the intersection IP distance a in the rotation direction upstream side in the tangential direction in the _two straight lines straight lines L ₂ is moved parallel L ₂ A point where 'and the pitch circle diameter Dp intersect is defined as a point O ₂ . The opposing side surface 41n and side surface 42n constituting the discharge groove 4n are arcs having different diameters R ₁ and R ₂ around the point O ₂ .

On the other hand, the length of the discharge groove 4n, that is, the position of the radially inner end of the discharge groove 4n is the tooth tip 21 _n-1 of the tooth part 2 _n-1 immediately before the discharge groove 4n in the rotation direction upstream. A point O _{1 that is} separated from the intersection point IP ₁ by a length b in the axial direction of the sprocket SP with reference to an intersection point IP ₁ of the straight line L ₁ connecting the center of the circumferential direction of the sprocket SP and the axis of the sprocket SP and the pitch circle diameter Dp. Is a position where a straight line L ₃ parallel to the tangent at the intersection point IP ₁ and an arc of diameters R ₁ and R ₂ centering on the point O ₂ intersect. In this way, the shape of each discharge groove 4 is determined.

  In addition, the shape of the discharge groove 4 in the front view shown in FIG. 1 is only required to be inclined in a curved shape from the root portion 24 toward the axial center toward the upstream side in the rotation direction. The length of the discharge groove 4 is not limited to the above form, and may be determined as appropriate in consideration of the size, thickness, material, and the like of the sprocket SP.

FIG. 3 shows a partial side view of the sprocket SP, and FIG. 4 shows a cross-sectional view taken along line BB of FIG. As shown in FIG. 3, discharge groove 4 has a substantially rectangular shape in side view, the width W of the discharge groove 4 (the difference between the diameter R ₁ and diameter R ₂ in FIG. 2), to the tooth pitch P It is preferably 30% or more and 40% or less. Moreover, the opposing side surface 41 and the side surface 42 which comprise the discharge groove | channel 4 may have the inclination that the width | variety of the discharge groove | channel 4 expands from the back side to the front side in FIG.

  Also, as shown in FIG. 4, the bottom surface 43 of the discharge groove 4 is preferably linearly shallower from the tooth bottom 24 toward the axial center, and the inclination angle θ is formed with the discharge groove 4 of the sprocket SP. It is preferably in the range of 10 ° to 20 ° with respect to the front side surface. When the inclination angle θ is less than 10 °, the effect of the present invention, that is, mud and sand are less likely to be removed from the meshing portion of the roller chain and the sprocket teeth 2 through the discharge groove 4, while the inclination angle θ is 20 This is because the strength of the tooth portion 2 and the discharge groove 4 may be lowered depending on the material of the sprocket SP if the angle exceeds. The depth d of the discharge groove 4 is preferably in the range of 30% to 50% of the maximum thickness of the sprocket SP.

  The tooth portion 2 formed on the outer periphery of the main body portion 1 is generally shaped according to the shape defined in JIS and ANSI. Specifically, if the chain pitch, the roller outer diameter, the number of teeth of the sprocket SP, etc. are determined, the pitch circle diameter, the root circle diameter, the tooth surface radius, the root arc radius, etc. are obtained from a predetermined formula and the tooth portion 2 shape is determined.

  A conventionally known material can be used as the material for the sprocket SP according to the present invention, but a material having high hardness is desirable from the viewpoint of improving durability. Examples of such materials include aluminum alloy, iron, titanium alloy, carbon steel, chrome molybdenum steel, and alloy tool steel. Moreover, you may use the thing which surface-treated and heat-processed with respect to these materials.

  The diameter of the sprocket SP according to the present invention is a diameter used for a two-wheeled vehicle, and is usually in a range of 50 mm to 310 mm. The thickness of the sprocket SP according to the present invention is a thickness used for a motorcycle, and is usually 4.3 mm, 5.8 mm, 7.2 mm, 8.7 mm, or the like.

  The sprocket SP according to the present invention can be manufactured by a conventionally known manufacturing method. For example, a step of punching a plate-shaped steel material into a disk shape, a cutting step of forming shaft holes 15 and fixing holes 16, and lightening holes 17 and 18 as necessary, inclined surfaces on the outer periphery of the front and back surfaces of the disk Turning process for forming 25a, 25b, gear cutting process for forming the tooth part 2 on the outer periphery of the disk, cutting process for forming the discharge groove 4 in the tooth bottom part 24 of the tooth part 2, heat treatment such as carburizing and quenching Examples thereof include a manufacturing method including a process and a finishing process such as deburring. In the case of such a manufacturing method, the cross-sectional shape, width W, inclination angle θ and the like of the discharge groove 4 can be adjusted by cutting using a cutting machine such as an end mill.

  It should be noted that the processing from the plate-shaped steel material into a disk shape and the formation of the shaft hole 15, the fixing hole 16, and the lightening holes 17 and 18 may be performed by cutting instead of punching. According to the punching process, high production efficiency can be obtained, but distortion remains in the punched product, which may affect the dimensional accuracy of the sprocket SP. On the other hand, a high dimensional accuracy can be obtained with the sprocket SP manufactured by cutting.

(Other)
Although the embodiment described above is a driven sprocket for a motorcycle, the sprocket according to the present invention is also applicable to a drive sprocket. Moreover, it is applicable also to the sprocket which has the tooth | gear part 2 of the shape which does not conform to JIS and ANSI.

  In the embodiment described above, the discharge groove is formed only on the front side surface, but it may be formed only on the back side surface, or may be formed alternately on both the front side surface and the back side surface in the circumferential direction, for example. It doesn't matter.

  According to the sprocket according to the present invention, mud, sand and the like between the teeth of the roller chain and the sprocket are removed through the discharge groove, and accumulation and solidification of mud and sand are effectively suppressed and useful.

DESCRIPTION OF SYMBOLS 1 Body part 15 Shaft hole 16 Fixing hole 17 Lightening hole 18 Lightening hole 2 Tooth part 21 Tooth tip 24 Tooth bottom part 25a, 25b Inclined surface 4 Discharge groove 41,42 Side surface of discharge groove 43 Bottom surface of discharge groove d Discharge groove Maximum depth W Maximum width of discharge groove P Tooth profile pitch SP Sprocket

Claims (7)

A disc-shaped sprocket for a motorcycle,
A sprocket having a discharge groove inclined in a curved shape on the upstream side in the rotational direction from the root to the axial center on at least one of the front and back surfaces.   The sprocket according to claim 1, wherein the discharge groove has a quadrangular shape in a side view.   The sprocket according to claim 1 or 2, wherein a bottom surface of the discharge groove becomes linearly shallower from a tooth bottom portion toward an axial center.   The sprocket according to claim 3, wherein an inclination angle of a bottom surface of the discharge groove with respect to a front surface or a back surface on which the discharge groove is formed is in a range of 10 ° to 20 °.   The sprocket according to any one of claims 1 to 4, wherein the discharge groove has an arc shape, and two opposing side surfaces constituting the discharge groove are concentric circles having different radii.   The sprocket according to any one of claims 1 to 5, wherein the maximum width of the discharge groove is not less than 30% and not more than 40% of the tooth profile pitch.   The sprocket according to any one of claims 1 to 6, wherein the discharge groove is formed only on one side of the front surface and the back surface.